"Break the "traditional" bike fitting rules"? What are you talking about?

I always put my foot on the ground without getting off the saddle when I have to wait for the light. However, I don't see why this waiting posture should immediately imply an improperly fit bike. My bike is fit perfectly, in full accordance with "traditional" bike fitting rules (in fact, I believe my seatpost is extended a bit higher than "traditional" rules require). Yet, I have no problem reaching to the ground with my toes without getting off the saddle.

In general case this will, of course, depend on how far the BB is from the ground and how long your crank is. But for a typical road bike proper "traditional" fit should not preclude anyone from being able to put their toes on the ground without getting off the saddle. My bike is actually a cyclocross[-ish] one, which usually means a greater BB-to-ground distance, but I have no problems with this anyway.

On my bike, when I support it with my toes, I don't even have to lean it much. Putting my entire foot on the ground would require a notably greater amount of lean, of course.

I can imagine that a person with some medical condition that restricts his/her ability to support their weight with their toes or pivot their foot downwards might have problems using this waiting technique. And, as a consequence, such person might opt for lower seatpost position, resulting in an improperly fit bike. But other than that I don't see where the idea of "improper fit" could come from.

P.S. If one's wearing "attached" cycling shoes, getting off the saddle to wait for a light usually means having to perform a straddling start afterwards. This is a major no-no in my book. Straddling start is reserved for children learning to ride a bicycle, and for women wearing non-cycling clothing. Cyclists don't do straddling starts. For an adult, properly equipped cyclist straddling start is considered an embarrassing thing to do.